Gun construction for gas blast spraying heat-fusible materials



Nov. 17, 1953 c. K. WILSON GUN CONSTRUCTION FOR GAS BLAST SPRAYINGHEAT-FUSIBLE MATERIALS 2 Sheets-Sheet 1 Filed Dec. 7, 1948 m a l n N H)JNVENTOR Cfia/rZesK M15071, 47

mm N Q N) mm mm, m Q Q mm N IIMW w U Q Nov. 17, 1953 c, w 5o GUNCONSTRUCTION FOR GAS BLAST SPRAYI HEAT-FUSIBLE MATERIALS 2 Shasta-Sheet2 Filed D80. 7, 1948 INVENTOR. Charles K ll zsm 67 8 I Patented Nov. 17,1953 UNITED STATES PAT NT FFECE GUN CONSTRUCTION FOR GAS BLAST SPRAYINGHEAT-FUSIBLE MATERIALS Application December 7, 1948, Serial No. 64,006

10 Claims.

This invention relates to improvements in gun construction for gas blastspraying heat-fusible materials.

Heat-fusible material spray guns of the gas blast type are devices inwhich such material is fed into a, melting zone in which it is melted,being thereafter expelled from the gun in subdivided form by a blast ofair or other gas. The materials to be sprayed may be fed into themelting zone either in the form of a rod or Wire or in the form ofpowder. A mixture of fuel gas and combustion supporting gas such as amixture of acetylene or propane and air or oxygen is fed to the meltingzone through suitable jets which discharge the combustible gas mixturewhich when ignited causes the melting of the material. When powder isused, the same may not always be completely melted as in some cases onlysome of the powder is melted, or some of the particles of powder may beonly partially melted or heat softened. In cases where a wire or rod isused, air or other gas is forcefully directed against the moltenmaterial at the tip of the rod or wire in such manner that it impingessharply against the tip to thereby substantially blast the material intofine particles. The construction of heat-fusible material spray guns ofthe gas blast type usually includes a combustible-gas nozzle or burnertip which is provided with a material feeding conduit and a multiplenumber of combustible-gas jets, substantially surrounding the axis ofthe feeding conduit, and a blast gas nozzle surrounding thecombustible-gas nozzle and the feeding conduit. In a gun construction ofthis type, the blast gas nozzle and the combustible-gas nozzle aremounted on a portion of the gun construction known as the gas head. Boththe combustible and the blast gases pass through this head to thenozzle. Such a gas head may be either an integral part of the gunconstruction involving the material feeding mechanism or it may be aseparate part of the gun. In either case, the gas head is the part ofthe gun assem bly upon which the blast gas nozzle and thecombustible-gas nozzle are mounted. It is to such construction that thisinvention primarily relates. Spray guns of the above described type areWell known for the spraying of metal, and for convenience the followingdescription is made in connection with metal spray gun constructions, itbeing understood that the principles of the invention are applicable toconstructions using other heat-fusible materials as, for instance,plastics.

One type of spray gun of the gas blast type which has been hitherto usedinvolves construction in which some part or parts of the gas head havebeen separate removable pieces, and in which the passages for thecombustible-gas and the combustion supporting gas have existed, at leastin part, in grooves or channels in such removable parts. In these, aportion of the head is removable from the remainder of the gas head.This construction has permitted grooving and drilling the removablesection, and drilling and, if desired, grooving the remaining portion ofthe gas head so as to produce practically any desired arrangement ofmixing chambers, mixing jets, and syphon jets and Venturi tubecombinations.

The diificulty with gas head constructions of this type with removablesections has always been, however, that no adequate or satisfactorymeans has ever been developed for sealing the removable portion to theremainder of the gas head. One method which has been used in the past inan attempt to solve this problem has involved the use of a removablesection of the gas head, provided with a tapered portion thereon, whichseats with a corresponding tapered seat in the remaining portion of thegas head. Construction of this type requires very strong holding meansto firmly hold the tapered portion in its taper seat. One typicalholding means for this purpose has been a threaded nut which screws onto a threaded stem extending from the removable section beyond itstapered portion. Such a fastening means, however, has required anadequate gas tight and heat resistant packing, and in a construction ofthis type it has been a common practice to use a solid copper metalpacking to seal between the threaded stem of the removable section ofthe gas head and the remaining portion of the gas head.

Construction of this type involving tapered seats and metal packings toseal between the removable section of the gas head and the remainingportion thereof have not proved satisfactory in the past. One reason forthis has been the fact that the tapered seats must fit very preciselyand consequently have been very expensive to manufacture and also tomaintain. Since the seats are metallic, the slightest scratch on eitherof the mating surfaces will cause serious and sometimes dangerous leaks.Another reason why constructions of this type have not provensatisfactory is clue to the fact that all burner tips are subject toflash-back which means that the fire will flash back inside of the jetopenings and burn at the point where the combustible-gas and combustionsupporting gas are first mixed.

Since this point of first mixture is inside the gas head, very intenseheat is generated within the head when flash-back occurs. This intenseheat frequently causes sufficient expansion of the fixed portion of thegas head to permit gas to leak across the tapered seat. Such intenseheat and subsequent cooling can also cause permanent deformation of themating seats produc ing a permanent leak between them.

A further disadvantage of these gas head constructions involving taperedseats and metallic packings is that the metallic packings do not permitready disassembly for cleaning and reassembly by the operator. Toperform this function of sealing, metallic packings, such as copperpackings, must be deformed each time they are tightened in place; andhence they make removal of the parts difiicult and usually requirereplacement of the packing upon each reassembly. Such packings are alsodangerous in that they are subject to improper sealing and hence subjectto leaks.

One object of this invention comprises, inter alia, a heat-fusiblematerial spray gun of the gas blast type construction which overcomesthe foregoing and other disadvantages.

A further object of this invention is a heatfusible material gas blastspray gun with a gas head construction comprising a removable portionand a remaining portion of such gas head which overcomes the foregoingand other disadvantages.

Another object of this invention is a gas blast gun gas headconstruction comprising a removable portion and a remaining portion ofsuch head which seals adequately and quickly between the two saidportions, and which avoids the use of tapered seats and metallicpackings.

Still another object of the invention is a spray gun gas headconstruction of the type referred to in which the removable portion ofsaid gas head is readil removable by the operator.

This and still further objects of the invention will be more thoroughlyunderstood from the following description read in conjunction with thedrawings illustrating a preferred embodiment of the structure inaccordance with the invention.

Fig. 1 is a central section taken longitudinally through the gas headpart of a gas blast gun in accordance with my invention;

Fig. 2 represents a section through the part of the gas blast gun shownin Fig. 1 in the plane IIII;

Fig. 3 is another section of the part of the gas blast gun shown in Fig.1 taken from the plane III-III;

Fig. 4 is another section of the part of the gas blast gun shown in Fig.1 taken from the plane IV-IV.

Referring to the Figs. 1, 2, 3 and 4, numeral I designates a removablegas head seat which in this construction is a removable portion of thegas head. The remaining, or fixed portion of the gas head, is designatedby numeral 2. Gas head seat portion I has a cylindrical outer surface at3 which fits the cylindrical bore of the fixed portion of the gas head2. The fit between these two cylindrical surfaces is a free or slidingfit with a very small amount of clearance between these surfaces at 3.

Gas head seat portion I has a longitudinal hole 4 through its centerwhich constitutes a conduit for the material being fed to the nozzle endof the gun for spraying. In the embodiment of this invention shown inthe figures, the material being fed to the flame is in the form of a rodor wire 5.

On the outer periphery of gas head seat portion I are three annulargrooves, 6, I, and 8, respectively. Mounted in these annular grooves arethree annular resilient packing rings, 8a, 9 and I0, respectively. Theserings have a section parallel to the ring axis which is normall circularwhen the rings are in a relaxed position. The annular grooves 6, I and 8are so proportioned, however, that when these resilient rings 8a, 9 andII! are in position in the grooves, they are compressed to an oval shapebetween the bottom of the grooves and the cylindrical bore of the fixedportion of the gas head 2.

In the particular embodiment of the invention illustrated in thefigures, the gas head seat portion I has a large annular groove I I. Italso has an annular groove I2 which extends into a narrower annularportion at I3. A multiple number of relatively small jets or passages I4are provided in gas head seat portion I extending parallel to the axisof seat portion I from annular groove I I to annular groove portion I3.Passages I5 extend in gas head seat I and parallel to the axis thereoffrom annular groove portion I3 to the forward end I6 of said gas headseat. There are the same number of passages I5 as there are jets I4, andeach passage I5 is in line with a corresponding passage I4.Combustible-gas nozzle I! is mounted on gas head seat I at its end I6.Nozzle I1 is provided with a multiple number of jets or passages I8which lead from end to end of said nozzle and which converge toward theflame end. Nozzle I1 is provided with an annular groove I9 at its baseor seat where it contacts gas head seat I at I8. Nozzle I1 is alsoprovided with a relatively hard bushing 20, permanently mounted in acentral longitudinal hole 2 I. Hole 2! acts as a conduit for wirematerial 5, and bushing 2!) acts as a guide for such wire.

The number of jets I8 may, if desired, correspond to the number ofpassages I5, or may be some other number. If desired, jets I6 maycorrespond in number to passages I5 and may also be 50 located that theentrance end of each jet I8 is in direct alignment with eachcorresponding passage I5. If desired, means may be provided (not shownin the illustrations) for locating nozzle IT, with respect to gas headseat I, so that such jet and gas passage alignment be assured. Suchalignment is not necessary, however, but in the event that suchalignment is not provided for, then annular groove I9 must besufiiciently large to provide for proper distribution of gas flowingfrom passages I5 to jets I8.

At one end of fixed portion of gas head 2 is provided a threaded plug 22which is threaded into fixed gas head. portion 2 at threads 23. Plug 22shoulders tightly against shoulder 24. A multiple number of holes 25 areprovided in plug 22 to permit the use of a spanner wrench for tighteningor loosening this plug. Centrally mounted in plug 22 is wire guide tube26.

A threaded clamping tube 21 is provided which threads directly intofixed gas head portion 2 at threads 28. This clamping tube is providedwith a shoulder 29 which clamps directly to the shoulder ofcombustible-gas nozzle I I. Clamping tube 2! is provided with a hexagonexternal shape to fit a wrench.

When clamping tube 21 is tightened in place it clamps nozzle I'I tightlyagainst face I6 of gas head seat portion I and simultaneously clamps gashead seat portion I firmly against plug 22 which forms a solid bottom orseat at the end 01' the cylindrical bore in fixed gas head portion 2.

Blast gas nozzle 30 is constructed with a conical internal bore which isspaced apart from the conical external surface of nozzle I! to form aconical passage 3!. Nozzle 39 has an extended external cylindricalportion 32 which fits into a corresponding bore 33 in clamping sleeve27. The end of nozzle 30 seats against shoulder 34 in clamping sleeve21. Blast gas nozzle clamping ring 35 is threaded on to fixed gas headportion 2 at threads 36' and clamps nozzle 30 in place by pressingagainst shoulder 3! of nozzle 30.

Gas space 38 is formed between clamping ring 35 and fixed portion of thegas head 2.

A multiple number of radial holes 39 are provided in clamping tube 21extendin radially therethrough at the point where shoulder 34 isprovided therein.

Slight annular grooves 40 and 4] are provided in the bore of fixed gashead portion 2 and are so located longitudinally that they are in linewith annular grooves H and I2, respectively. A gas passage 42 isprovided in fixed gas head portion 2 leading from a source of combustionsupporting gas (not shown) to annular groove 40. Gas passage 43 isprovided in fixed gas head portion 2 leading from a source ofcombustible-gas (not shown) to annular groove 4|. Gas passage 44 isprovided in fixed gas head portion 2 lead- T ing from a source of blastgas (not shown) to gas chamber 38.

In operation, the material to be sprayed is fed progressively in theform of a wire through wire guide tube 26, wire conduit 4, wire conduit2|, and through bushing 20, from whence it emerges into the flame zonein front of combustible-gas nozzle l1. A combustible gas such asacetylene is fed into passage 43 whence it flows into and fills annulargroove 12 and the extension l3 thereof. A combustion supporting gas suchas oxygen is fed into passage 42 from whence it flows into and fillsannular groove H. From annular groove II, the combustion supporting gasflows through the multiple jets l4 across annular groove portion l3 andinto passages I5. As combustion supporting gas flows across grooveportion l 3 it draws with it combustible-gas which also enters passagesI5. Both these gases are mixed as they flow through passages l5, forminga gas mixture of combustible-gas and combustion supporting gas. This gasmixture flows from passages i5, through a portion of annular groove isand into jets I8, from whence it emerges at the end of nozzle I! to burnand form the necessary heating zone.

Compressed blast gas, such as air, is fed into passage 44 from whence itflows into chamber 38, through multiple holes 39, and thence intoconical space 3!, where it emerges at the end of nozzle I! in the formof a cone of blast gas exterior to and surrounding the flame. As theblast gas continues to flow it emerges from the end of blast gas nozzle39 and converges upon the flame surrounding the end of the wire 5 at itsheated tip with sufilcient force to atomize the heat softened materialof said wire and to propel the atomized particles of material to thesurface being sprayed.

In normal spraying operations, the operator takes frequent occasion toremove the combustible-gas nozzle I! either for changing the noz zle toa difierent one to accommodate a different size wire, or for cleaningthe gasjets I8. To do this, the operator simply first removes theclamp-- ing ring 35 and picks off the blast gas nozzle 3.0, and thenremoves clamping tube 21 and picks off nozzle II. If. for any reason, heshould then desire to remove the gas head seat portion I, he may then doso by simply sliding it out of the cylindrical bore of fixed gas headportion 2. By pressing on the end of wire guide tube 26, the operatorcan easily force gas head seat portion I forward far enough so that itcan be easily pulled out from the front end. The removable mountin ofgas head seat portion I is such that usually but little pressure onguide tube 26 is required. Light tapping, however, may be sometimesrequired. It is necessary to remove seat portion l and clean thepassages in the event that a flash-back has occurred.

The resilient packing rings 8a, 9 and ID are preferably made of asynthetic rubber such as neoprene. The slight annular grooves 40 and 4|are provided so that these rings will slide easily past the port ends ofthe passages 42 and 43 when assembling or disassembling.

The very slight space or clearance between the cylindrical outer surface3 of gas head seat 1 and the corresponding bore of fixed gas headportion 2 is made as small as is practical but still permit easy slidingof the seat member within the bore. This very small clearance ismaintained so that only a very small amount of gas could leak acrossbetween the cylindrical portions of the seat plug l and the bore.

Tests have been conducted for leaks of constructions in accordance withthis invention which were purposely assembled with the resilient packingrings 8a, 9 and Hi omitted. It was found that no leaks sufficientlyserious to cause hazard in the normal operation of the equipmentdeveloped. These tests were made as a precaution since it is clearlyrecognized that the resilient packing rings may be of a material whichwould be deteriorated by the heat resulting from a flash-back in theequipment. It is one of the outstanding advantages of the constructionin accordance with this invention that the safety in use of thisconstruction does not depend upon the maintenance of the resilient ringsin good condition. The ring should, of course, be maintained in goodcondition, however, to obtain normal and eflicient operation of theequipment. Further tests have been conducted of a construction inaccordance with this invention wherein the resilient rings were properlyassembled and it was found that no leaks whatsoever developed across thesurfaces sealed by these rings. It should be noted that one of theadvantages of this construction lies in the fact that no tighteningmeans or other adjustment is provided for tightening these resilientpacking rings. These rings are sufficiently loose to permit easy slidingof the gas head seat portion l in the bore of gas head fixed portion 2.However, this construction is such that as pressure is applied to aresilient ring, the forces are such as to deform th ring so that itpresses still more firmly against the side of its annular groove andagainst the bore in gas head fixed portion 2. As the pressure increases,the ring is pressed still more firmly against the bore in gas head fixedportion 2 and against the corner or edge at the top of the side of theannular groove in seat portion I. The result is that the greater the gaspressure, the greater is the sealing pressure of the rings and hence noleak can develop.

Another advantage of the construction in accordance with the inventionis the fact that flash back can occur and the burning may continueinside the gas head for a considerable time without causing seriousdamage to the equipment. In no case will any serious warpage of th metalparts occur which will prevent proper sealing since the final sealing isby means of the resilient packing rings. In fact, the fire may burninside the gas head for some little time without damaging these ringsdue to the high rate of heat conductance of the metal in the gas head.Even if the rings are eventually damaged they may be easily and quicklyreplaced and are by their nature inexpensive.

Throughout the foregoing description reference has been made to thematerial to be sprayed as being in solid wire form. This sameconstruction is readily adaptable, however, when spraying material whichis in granular form, such as in the form of a powder. In such cases, thefinely divided material is conveyed through the central hole in wireguide tube 26, through conduits 4 and 2!, and out through the hole inbushing to the heating zone in front of nozzle [1. Such finely dividedmaterial may be thus conveyed either in the form of relatively packedmaterial or may be conveyed by means of a carrier stream of gas.

While the structures shown in the illustrations are necessarilyspecific, my invention applies broadly to gun construction for gas blastspraying heat fusible materials and preferably metal, and essentiallycomprises the improvement therein of a gas head for said gun having afirst portion with a substantially cylindrical bore surface and a secondportion with a substantially cylindrical outer surface substantiallyfitting said bore surface, first gas duct means for combustible gas and,second gas duct means for combustion supporting gas in each of saidfirst and second portions, each of said duct means terminating at one ofsaid surfaces with said first duct means in said first and secondportions in gas passing registry with each other and said second ductmeans in said first and second portions in gas passing registry witheach other, at least one annular groove on at least one of said surfacesbetween the terminal portions of said first and second gas duct meansthereon, at least one resilient packing means in said groove compressedtherein between said first and second portions, and. means for removablyholding said second portion in substantially fixed gas duct registryposition with said first portion.

Thus, within the broadest concept of the invention the annular groovesfor holding the packing means and preferably resilient packing rings of,for instance, synthetic rubber, may be cut into the bore of fixed gashead portion 2 or into the external surface of gas head seat portion I,or, may be out part way into each of these surfaces. Within thepreferred embodiment of the invention shown, however, it is preferred tocut the grooves into the external surface of gas head seat portion I.

While the construction illustrated shows the seat portion l with asingle diameter for the outer cylindrical surface at 3, it is obviousthat this outer surface may, if desired, be made with several diametersof cylindrical surfaces and that the bore in fixed portion 2 would alsohave different diameters to correspond to the outer surfaces of the seatportion I. As an example, the cylindrical surface adjacent the ringgroove farthest from the gas head nozzle could, if desired.

be of a different diameter than the cylindrical surfaces adjacent theother ring grooves.

The removable gas head seat portion I is made of a single piece in thepreferred embodiment of this invention and is so illustrated in thefigures. If desired, such as for convenience of manufacture, it may bemade in two or more pieces within the scope of this invention.

While the foregoing description was made with reference to a particularjet construction for mixing and conveying combustible-gas and combustionsupporting gas, it is obvious that this part of the construction can bevaried as desired, and that any suitable means of conveying and mixingthese two gases may be used in the construction in accordance with thisinvention. It is also evident that any suitable gas blast nozzleconstruction desired and any suitable combustiblega nozzle constructionmay be used as desired in the construction in accordance with thisinvention.

The foregoing description is furnished by way of illustration and not oflimitation, and it is therefore my intention that the invention belimited only by the appended claims or their equivalents wherein I haveendeavored to claim broadly all inherent novelty.

I claim:

1. Improvement in gun construction for gas blast spraying heat fusiblematerials comprising a gas head for said gun having a first portion witha substantially cylindrical bore surface and a second portion with asubstantially cylindrical outer surface substantially fitting said boresurface, first gas duct means for combustible gas and second gas ductmeans for combustion supporting gas in each of said first and secondportions, each of said duct means terminating at one of said surfaceswith said first duct means in said first and second portions in gaspassing registry with each other and said second duct means in saidfirst and second portions in gas passing registry with each other, atleast one annular groove on at least one of said surfaces between theterminal portions of said first and second gas duct means thereon, atleast one resilient packing means in said groove compressed thereinbetween said first and second portions, and means for removably lockingsaid second portion in substantially fixed gas duct registry positionwith said first portion.

2. Improvement in accordance with claim 1 in which there are providedadditional annular grooves on at least one of said surfaces, each havingat least one of said packing rings therein and at least one of saidadditional grooves and rings being positioned between each end of saidsecond portion and the thereto nearest terminal gas duct portionthereon.

3. Improvement in accordance with claim 2 in which said annular grooveis provided on the cylindrical outer surface of said second portion.

4. Improvement in accordance with claim 3 in which said packing meansare at least one packing ring for each of said grooves.

5. Improvement in gun construction for gas blast spraying heat fusiblematerials comprising a gas head for said gun having a first portion witha substantially cylindrical bore surface and a second portion with asubstantially cylindrical outer surface substantially fitting said boresurface, first gas duct means for combustible gas and second gas ductmeans for combustion supporting gas in each of said first and secondportions, each of said duct means terminating at one of said surfaceswith said first duct means in said first and second portions in gaspassing registry with each other and said second duct means in saidfirst and second portions in gas passing registry with each other, atleast one annular groove on at least one of said surfaces between theterminal portions of said first and second gas duct means thereon, atleast one resilient packing means in said groove compressed thereinbetween said first and second portions, additional annular grooves on atleast one of said surfaces, each having at least one of said packingrings therein and at least one of said additional grooves and ringsbeing positioned between each end of said second portion and the theretonearest terminal gas duct portion thereon, combustible gas jet ducts insaid second portion supplied by said first and second gas ducts, andmeans for removably holding said second portion in substantially fixedgas duct registry position with said first portion, said holding meansincluding a combustible gas nozzle removably seated against one end ofsaid second portion with its gas jet ducts in gas passage registry withthe gas jet ducts of said second portion, stop means carried by saidfirst portion positioned for retaining said second portion againstmovement away from said nozzle, and means secured to said first portionfor clamping said second portion between said nozzle and said stopmeans.

6. Improvement in accordance with claim in which said annular groove isprovided on the cylindrical outer surface of said second portion.

7. Improvement in accordance with claim 6 in which said packing meansare at least one packing ring of synthetic rubber for each of saidgrooves.

8. Improvement in accordance with claim 5 in which said second portionand said nozzle define a heat fusible material feeding conduit, in whichsaid stop means substantially define a plug carrying a wire feed bushingadjacent said second portion in registry with said feed conduit, and inwhich said bushing is slidable in the direction of said second portionand secured against mo tion away from said second portion.

9. Improvement in accordance with claim 8 in which said annular grooveis provided on the cylindrical outer surface of said second portion.

10. Improvement in accordance with claim 9 in which said packing meansare at least one packing ring of synthetic rubber for each of saidgrooves.

CHARLES K. WILSON.

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